The purpose of this project is to gain an improved understanding of the transformations that occur in the subsurface downstream of on-site wastewater disposal systems and septic systems. These systems are used widely throughout the United States to treat and discharge wastewater effluent. The approach involved the collection of samples from a septic research center in Cape Cod, MA, and analysis of these samples for nitrogen, phosphorus, dissolved oxygen, pH, alkalinity, suspended solids, metals, and other water quality parameters. Inverse modeling was used to compare samples collected upstream and downstream of subsurface “leaching” fields consisting of sand beds. This approach provided a basis to identify key reactions occurring in the subsurface downstream of the discharge. In addition, a reactive transport software package, based on the PHREEQC and Hydrus-1d models, was used to model the transport in these sand beds and identify possible reactions and changes in contaminant concentrations with depth. To understand the implications of the discharges, an additional field study was completed in an area where septic systems have impacts on surface waters. Samples collected from a stream provided an indication of the loads entering the stream as a result of septic system discharges. Combining the results from the modeling with the results of this field investigation provided an approach to estimate the transport of nutrients and other contaminants entering the surface waters from septic system discharges. The results provide a basis for understanding the impacts of septic systems on surface waters, and develop better approaches for reducing the impacts of these discharges.

Gasoline spills are sources of groundwater contamination. In the event of a spill, timely remediation efforts can advert most of the potential groundwater contamination due to the immiscibility of gasoline in water. Ethanol functions as a cosolvent that can increase the solubility of gasoline in water. Therefore, the risk of groundwater contamination in the event of a fuel spill increases as the ethanol content in automobile fuels increases. This study examines the effect fuel spill size and ethanol content has on the quantities of toluene, ethylbenzene, m-xylene and o-xylene (TEMO) that dissolve into the aqueous phase at equilibrium. Laboratory experiments were preformed to determine the mass fractions of TEMO in waters that were in contact with various volumes of gasoline and ethanol. UNIFAC is a model capable of predicting the concentrations of TEMO in the aqueous phase of a gasoline-ethanol-water system at equilibrium. In this study, the generalized UNIFAC-LLE method, designed for chemical engineering applications, was used to model the laboratory experiments. New UNIFAC-LLE parameters were developed to improve the model's accuracy in predicting the solubilities of aromatic species in ethanol-water mixtures. The new UNIFAC-LLE parameters were also used to model the laboratory experiments. The modeled results were compared to the analogous laboratory experiments. The UNIFAC-LLE parameters developed in this study improved the model's accuracy in predicting the solubilities of TEMO when the aqueous ethanol mass fraction was between 0.114 and 0.431.

Methyl Tertiary-Butyl Ether (MTBE) contamination of groundwater and surface waters has become a relevant environmental and public safety concern in recent years. This anthropogenic compound is now persistent at low concentrations in several valuable ground and surface water locations within the United States due largely to the widespread production of MTBE for use as a fuel oxygenate in conjunction with negligent underground storage practices during the 1980's and 1990's. Though there are several treatment strategies for the remediation of MTBE spill sites, the most efficient strategy may be adsorption of MTBE by a packed column of silicalite-1 adsorbent. Effective adaption of this technology requires cheap production of silicalite-1 sorbent packing particles on the order of 3 millimeters diameter. This work entails the development of a new synthesis process which results in sufficient in-situ crystallization of silicalite-1 aggregates within a 3 millimeter spherical amorphous silica gel source. The crystal aggregates sizes can be tuned from 5 to 70 µm, depending on synthesis parameters, and the finished silicalite-1 aggregate particle takes the shape of the amorphous gel source. These aggregate particles, when containing a small amorphous core, should be suitable for packed adsorption column applications. Multiple hydrothermal synthesis experiments were performed by batch methods featuring silica gel spheres as the sole silica source for the batch. Zeolite nucleation and crystal growth were demonstrated throughout the amorphous bead. Synthesis parameters were optimized both for short synthesis times, optimal mechanical properties, and cost effectiveness. The influence of product crystal size on particle hardness was also investigated. The packing production process is sufficiently ready for supporting pilot scale adsorption studies.

Stormwater runoff from urbanized areas can have detrimental impacts on groundwater and surface water supplies by mobilizing contaminants such as bacteria and nutrients from surrounding areas. Best Management Practices (BMPs) are commonly designed to mitigate these impacts, but the processes governing the effectiveness of these BMPs are often not well understood. Biofiltration BMPs, which include storage, sediment removal, and infiltration processes, are particularly challenging to quantify. This research involved an investigation of the processes associated with a biofiltration BMP located in West Boylston, MA adjacent to the Wachusett Reservoir. The basin treats runoff from an 8-acre watershed with two roadways (Routes 12 and 110) and surrounding residential and commercial land uses. Water exits the basin by either seepage directly to groundwater or by seepage through a two-foot filtration bed to an outfall pipe on one side of the basin. A field sampling program was conducted in collaboration with the Massachusetts Department of Conservation and Recreation to characterize the various flow paths of contaminants upstream, within, and downstream of the biofiltration facility. The program included collection of volumetric flow information, field parameters (dissolved oxygen, specific conductance, pH, and temperature), and water quality samples. Samples were tested for alkalinity, bacteria, dissolved organic carbon, nutrients, additional anions and cations, and suspended sediments. Stormwater samples were collected for storm events that included substantial rainfall and illustrated seasonal variability. A set of seven monitoring wells installed for this project provided information on groundwater flow and quality at the site. The field program provided quantitative data on the flows and transformations that occur within and in the groundwater downstream of the biofiltration basin. The results demonstrated that stormwater infiltration to groundwater is an important component to consider for BMP design. The flow path through the outfall was effective in removing sediments, but was found to have limited capacity for water quality treatment, since only small changes in stormwater quality occurred between the culvert inflow, basin, and outfall samples. However, analysis of the flow data showed that infiltration to groundwater was comparable to discharge through the outfall. Furthermore, the signatures of stormwater infiltration could still be seen in the wells, indicating that the infiltration from the stormwater basin can impact groundwater quality. The groundwater pathway was found to impact the chemistry of the constituents, and was particularly effective in removing bacteria and phosphorus. The results demonstrate the value of groundwater recharge as a component of BMP design, and provide a basis for a number of specific design recommendations related to biofiltration basins.

The increase in irrigated agriculture in Saudi Arabia is having a large impact on its limited groundwater resources. While large-scale water storage changes can be estimated using satellite data, monitoring groundwater abstraction rates is largely non-existent at either farm or regional level, so water management decisions remain ill-informed. Although determining water use from space at high spatiotemporal resolutions remains challenging, a number of approaches have shown promise, particularly in the retrieval of crop water use via evaporation. Apart from satellite-based estimates, land surface models offer a continuous spatial-temporal evolution of full land-atmosphere water and energy exchanges. In this study, we first examine recent trends in terrestrial water storage depletion within the Arabian Peninsula and explore its relation to increased agricultural activity in the region using satellite data. Next, we evaluate a number of large-scale remote sensing-based evaporation models, giving insight into the challenges of evaporation retrieval in arid environments. Finally, we present a novel method aimed to retrieve groundwater abstraction rates used in irrigated fields by constraining a land surface model with remote sensing-based evaporation observations. The approach is used to reproduce reported irrigation rates over 41 center-pivot irrigation fields presenting a range of crop dynamics over the course of one year. The results of this application are promising, with mean absolute errors below 3 mm:day-1, bias of -1.6 mm:day-1, and a first rough estimate of total annual abstractions of 65.8 Mm3 (close to the estimated value using reported farm data, 69.42 Mm3). However, further efforts to address the overestimation of bare soil evaporation in the model are required. The uneven coverage of satellite data within the study site allowed us to evaluate its impact on the optimization, with a better match between observed and obtained irrigation rates on fields with higher frequency of available data. The inclusion of novel remote sensing sources (e.g. CubeSats) that offer higher frequencies and higher resolution can also be explored to improve the methodology, although further validation of these systems is needed. The developed framework has the potential to be used as a water management tool to monitor groundwater losses over large remote regions.

A crescente importância da questão do uso sustentável da água e a conseqüente necessidade de se diminuir a poluição e o desperdício desse reservatório terrestre, impulsionaram esse estudo. O objetivo principal do trabalho é avaliar a aplicação de indicadores isotópicos ambientais, como Sr, Pb, O e D, para estudos da origem e qualidade da água de recarga de um aqüífero, bem como do impacto da impermeabilização da superfície da cidade sobre esses indicadores. Para isso foram escolhidas duas áreas na Bacia do Alto Tietê, na Cidade de São Paulo, uma na Zona Oeste (área 1 - USP) e outra na Zona Leste (área 2 - VE), onde foram coletadas amostras de água da SABESP, de água de chuva e de poços de monitoramento, por um ano, além de sedimentos. Foram realizadas análises químicas em 390 amostras de água e 62 de solos, além de 413 análises isotópicas de H e O e 122 de Sr e Pb em água, além de 34 de Sr e Pb em sedimento. A determinação de procedimentos químicoanalíticos, para análises isotópicas de Pb e Sr em águas com baixas concentrações destes elementos, foi o primeiro resultado deste trabalho e definiu que as amostras devem ser filtradas e acidificadas, antes da evaporação, e seus resíduos devem ser dissolvidos com HCl, HNO3 e HF, para depois a amostra ser purificadas por resina de troca iônica. Todas as amostras de água subterrânea apresentaram alguma contaminação antrópica. Os poços da VE apresentaram contaminação caracterizada por altas concentrações de cloreto, sulfato e nitrato e a USP de cloreto, sulfato, amônio, sódio e fluoreto, além de elevada alcalinidade. Os lixiviados de Pb em sedimentos mostraram que há pouca interação destes com a água subterrânea e esses não foram utilizados como membros finais da mistura. As análises isotópicas (H e O) das chuvas indicaram que as precipitações da Cidade de São Paulo sofrem influência tanto do efeito quantidade, quanto das diferentes origens de massas de ar em diferentes períodos do ano. A estimativa de recarga utilizando os isótopos mostrou que a VE, mais impermeável, apresentou uma contribuição antrópica 10% (H e O) a 20% (Pb) maior do que a USP. Na USP, a recarga natural calculada por isótopos de H e O possui uma média de 70%, enquanto na VE esse valor cai para 59%. Os isótopos de Pb forneceram médias de 53% e 35%, respectivamente para USP e VE, de recarga natural. Diante dos cálculos efetuados e análises (químicas e isotópicas) concluiu-se que os isótopos de Sr não são indicados para traçar a recarga de áreas contaminadas, já que mostram pouca interação entre a rocha e a água. Os isótopos estáveis não apresentaram muita diferença entre as assinaturas de água da SABESP e das amostras mais contaminadas por esgoto e não são bons diferenciadores dessas duas fontes. Já os isótopos de Pb são bons indicadores de recarga para áreas contaminadas, porque conseguem discriminar as águas oriundas de fugas da rede da SABESP e do esgoto. / The importance of a sustainable use of water and its resultant necessity of reducing groundwater pollution and waste is the driving force of this study. The main subject is to evaluate the application of environmental isotopes, as H, O, Sr and Pb, for studying the groundwater recharge sources and its quality, as well as the impact of the surface sealing on these indicators, due to urbanization. Two areas with different occupation in São Paulo City, within the Upper Tietê Watershed, one in west zone (area 1) and other in the east zone (area 2) were chosen to do this study. In both areas, water samples were collected for a year from: monitoring wells, supply agency and rain. Sediments were also sampled during drilling. Chemical analyses were carried out in 390 water samples and 62 sediments, whereas H and O isotopic analyses were performed on 413 water samples and Pb and Sr isotopic analyses on 122 water samples and 34 sediments. This work also determined that analytical procedures for Pb and Sr isotopic analyses of groundwater samples with low Sr and Pb concentration should filter and acidify water samples prior to evaporate it, their residue should be dissolved with HCl, HNO3 and HF, before purification by ionic exchange resin. All groundwater samples showed some anthropogenic contamination. Groundwater contamination in VE is characterized by high concentrations of Cl-, SO42- and NO3-, whereas in USP of Cl-, SO42-, NO3-, Na+ and F- besides high alkalinity. The Pb leaching isotopic technique applied on sediments showed that there is low water-rock interaction and they were not used as end members for the mixing calculation. The H and O isotopic analyses indicated that precipitation in São Paulo are dependent of the amount effect and the different sources of air masses in different climate periods. The isotopic estimate of recharge indicated that VE, which has a more impermeable surface, has approximately 10% (H e O) to 20% (Pb) more anthropogenic recharge than USP. At USP the natural recharge calculated by H and O isotopes has mean value of 70%, whereas in VE this value drops to 59%. The Pb isotopes indicated a natural recharge of 53% and 35% for USP and VE, respectively. The conclusions made with the isotopic and chemical results are that: Sr isotopes are not good recharge tracers for contaminated areas with low residence time; O and H isotopes do not present significant differences between isotopic signatures from water distributed by the public supply company and most contaminated samples by sewage; Pb isotopes are good indicators of recharge tracers for contaminated areas, as they can discriminate waters from sewer leakage and public supply company waters.

Orientador: Rodrigo Lilla Manzione / Banca: Diego Augusto de Campos Moraes / Banca: Márcia Pereira Sartori / Banca: Didier Gastmans / Banca: Mauricio Moreira dos Santos / Resumo: A geoestatística permite inferir valores desconhecidos que apresentam estrutura espacial, auxiliando, assim, na descrição dos fenômenos naturais. A utilização de seus interpoladores permite um melhor entendimento do objeto de estudo, pois seu embasamento matemático garante a confiabilidade do método e sua utilização associada ao entendimento físico do problema proporciona resultados significativos. As ferramentas geoestatísticas vem sendo amplamente utilizadas no monitoramento e nos estudos dos recursos hídricos. Partindo-se da hipótese de que os níveis de água subterrânea podem ser explicados por um modelo determinístico e espacializados por ferramentas da geoestatística, o trabalho teve como objetivo o mapeamento do lençol freático através de um modelo híbrido de regressão-krigagem. Dados relacionados ao relevo, ao solo, às series de monitoramento da água e à vegetação, obtidos por sensoriamento remoto, totalizaram 21 variáveis preditivas dos níveis do lençol freático. As informações sobre as águas subterrâneas foram coletadas por meio de 56 piezômetros e as informações sobre os solos foram coletadas em 113 pontos amostrais distribuídos irregularmente nas bacias hidrográficas dos rios Guarantã, Bugre, Boi, Santana e Passarinho. A seleção das variáveis de maior relevância para o ajuste do modelo de regressão linear foi realizada por meio da análise de componentes principais, que determinou aquelas com maior variabilidade. Os resultados mostraram robusto ajuste aos dados pelo... (Resumo completo, clicar acesso eletrônico abaixo) / ABSTRACT: Geostatistics allows inferring unknown values with spatial structure, supporting the natural phenomena description. Geostatistical interpolators increase the understanding about the studied object, since its mathematical background ensures reliability to the method and its use associated to the physical understanding of the problem provides significant results. Geostatistical tools have been widely used in groundwater monitoring and studies. From the hypothesis that groundwater levels can be explained by a deterministic model and spatialized with geostatistics, this work aimed to map the water table through a hybrid regression-kriging model. Soil, topographic, water and vegetation monitoring data (obtained by remote sensing) were used as predictive variables of groundwater levels. Information were collected at Guarantã, Bugre, Boi, Santana and Passarinho watersheds. The most relevant variables for the multiple regression model were chosen through principal components analysis, which determined those with greater variability. The results indicated a robust fit to the data by the model and robust predictive capacity for new observations. The adjustment of the variograms allowed the ordinary kriging of the mean water levels and the residuals of the deterministic model, allowing a final prediction map of the groundwater. / Doutor

No description available.

This thesis presents studies of the heterogeneous nature of groundwater-surface water (GW-SW) interactions at the hillslope and catchment scale in the 3.2km2 Bruntland Burn, UK. GW fluctuations were measured within three contrasting hydropedological units. Synoptic hydrogeochemical surveys were carried out (major ions, stable isotopes) to capture the increased influence of GW to the stream during a 10year return period drought. The catchment was shown to have highly dynamic GW stores, with each landscape unit translating into different rainfall-runoff processes. Soil characteristics were shown to be the strongest predictors for variability in GW dynamics. Each soil type was characterised by a unique storage-discharge relationship and threshold response with a certain GW level above which lateral flow dominated. On the lower hillslope, predominating lateral flow and little recharge to depth is supported by hydrologically responsive soils. Connectivity between the steeper slopes and the valley bottom, however, needed persistent wet periods to overcome storage thresholds. Here, vertical flow paths recharging deeper GW dominated, with GW levels falling below the soil layer into the underlying drift. It was found that relatively well mixed, near-surface sources of stream flow predominated in wetter conditions, whilst baseflows are variable and reflect a diverse range of GW stores. Geophysics (ERT) and GW level measurements were integrated into MODFLOW-NWT to simulate GW-SW interactions along a representative 2D-hillslope transect. Although only a preliminary model, it was shown that shallow pathways have much shorter residence times, thus maintaining high water tables in the riparian peatlands, than deeper flow paths discharging through the drift and directly into the stream. Largest sources of GW are located within the drift, resulting in complex spatial patterns of runoff generation. This work illustrated the utility of a basic model to predict GW flow paths, highlighting how water and solutes are stored and released in montane headwater catchments.

Resumo: O presente trabalho tem como objetivo o estudo hidrogeológico do Sistema Aqüífero Tubarão na região central aflorante do Grupo Tubarão no Estado de São Paulo, visando a caracterização das rochas reservatório e a qualidade de suas águas. Para isso, montou-se um banco de dados com informações de poços, descrições petrográficas e ensaios petrofísicos de amostras. Os dados de poços indicaram maior predominância de arenitos na região centro-oeste da área, entre os municípios de Tietê, Capivari e Elias Fausto. A menor ocorrência de rochas reservatórios para água foi registrada na borda leste e na região nordeste do estado. As análises das características permo-porosas, extraídas de dois poços, indicaram grandes variações das condições de fluxo, influenciadas pela granulometria e seleção e, secundariamente, pela cimentação da rocha. A análise hidroquímica apontou a presença de águas bicarbonatadas cálcicas e sódicas na área, com discreta predominância de águas cálcicas junto à borda da bacia, e sódicas em direção a seu interior. O fluxo de água subterrânea ocorre da região de recarga, posicionada na borda leste da bacia, convergindo para oeste em direção aos principais rios da região. Por fim, a análise de favorabilidade indicou a região de Tietê como a de melhores características para a exploração de água subterrânea. / Abstract: This hydrogeology study defines both the reservoir rock character and the water quality of the Tubarão Aquifer System in São Paulo State, Brazil. This was done with the assistance of an extensive well information database coupled with petrographic, petrophysical, and hydrochemical analyses. The well data indicates high sandstone predominance in the west-center region of the study area, close to the cities of Tietê, Capivari and Elias Fausto. In the east and northeast regions of the state there is very little aquifer data available. Petrophysical and petrographic analysis from two wells indicated high variations in flow conditions, a function of differing grain size and sorting and secondary by the presence of pore filling cement. The hydrochemical analysis revealed a mainly bicarbonated calcic and sodic water composition in the study area. There was a discreet tendency towards calcic waters along the boundary to a tendency towards sodic water in the interior of the system. The aquifer is recharged in the east boundary region of the system and converges to west toward the main rivers in the study area. Finally, the favorability analysis demonstrated that the Tietê region is among the most favorable areas for additional groundwater exploration. / Orientador: Chang Hung Kiang / Coorientador: Maria Rita Caetano-Chang / Banca: Aldo C. Rebouças / Banca: Setembrino Petri. / Banca: Sidnei Pires Rostirolla / Banca: Uriel Duarte / Doutor